Cycle UI is a desktop tool to read out and visualize the data from a stationary bicycle. This way, you can place a laptop over the bicycle computer and yet be able to monitor your progress. The connection to the bicycle is established with a Digispark microcontroller.

So far, the UI features the following basic functionality, displaying

• active ride time, i.e., time spent on the bicycle during which the wheels were actually turning,
• speed, which is really just a guesstimate calculated from
• revelations per minute,
• and the total number of revelations.

In addition, speed is plotted on a graph to keep me motivated. Here's a quick screenshot of the UI in action, shown above a random YouTube cycling video:

The overlay stays on top and is quite unintrusive.

Python

• pySerial (tested with version 2.6)

For the microcontroller

• Digispark or some other Arduino-like board
• 3.5mm stereo audio jack
• 10K ohm resistor (for pulldown)

In addition, you need to install some of the "DSEG" fonts.

Upload the cycle.ino sketch onto a Digispark. Any other Arduino will also work with slight modifications to the serial commands.

Then connect the Digispark to your computer (via the primary USB port) and start the UI:

python ui.py

Depending on your OS settings, you may have to change USB permissions for this to work.

Somewhere inside the bicycle, a switch closes at a fixed point during each revolution. My bicycle (of the renowned "Ultrasport" brand) has a 3.5mm stereo headphone jack connecting the bicycle internals to the stock computer. Unfortunately, the switch does not make use of the ground wire but instead connects to the left and right channel.

I simply connected these to the pin #2 and 5v on the Digispark. I further added a pulldown resistor between pin #2 and ground. The Digispark counts revolutions and measures the time between, from which the UI calculates speed and distance.